<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script>

function boom()
{
    var s = document.createElementNS("http://www.w3.org/1999/xhtml", "span");
    var b = document.createElementNS("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul", "box");
    s.appendChild(b);
    document.getElementById("a").appendChild(s); 
}

</script>
</head>
<body onload="boom();" style="-moz-column-width: 1px;"><span id="a"><box xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"/></span><div>Hello</div></body>
</html>
